db2 query optimization

In SQL, query conditions need to be divided into three types in the query optimization stage. The three types of conditions have different effects and can be converted to each other in some cases.First, describe the SQL statement execution steps, which can be divided into three steps: 1. Read the tuples in the table; 2. If join exists, join is started; 3. filter

For more information on how to add DB2 coordinates in a MAVEN project, see: Https://www.cnblogs.com/zifeiy/p/7918554.html The contents of the Application.properties file in the Spring boot project are as follows: # DB Configuration for DB2 spring.datasource.url=jdbc:db2://localhost:50000/SAMPLE spring.datasource.username=zifeiy spring.datasource.password=izzzyc spring.datasource.driver-cl

Tags: db DB2Materialized view of DB2 a table based on the definition of a query result, which contains data from one or more tables on which the definition of the base is based, the use of which can significantly improve the operational performance of the query.Both the view and the base of the database are defined based on a single query. The

Tags: using ar sp data div art on BS sizePaged query statements that are used in different databases:Current page: CurrentPagePage Size: pagesize1. Oracle DatabaseSELECT * FROM (select A.*,rownum rn from (query_sql) A) where Rn Note: query_sql is a query SQL statement.OrSELECT * FROM (select RowNum rn,id from TABLENAME where RowNum 2. Infomix DatabaseSelect Skip CurrentPage First pagesize * from TABLENAME3.

Tags: put query--persistent enc mybatis prevent ace EPODB2 Startnum: Start number Endnum: End NumberSQL statement ? SELECT * FROM ( SELECT B.*, ROWNUMBER() OVER() AS TN FROM ( SELECT * FROM 表名 ) AS B ) AS A WHERE A.TN BETWEEN startNum AND endNum; 1 2 3 4 5 6 7 8 As shown above, this is a paged query statement for

deptno, avg (SAL) from EMP WHERE Deptno in (a) GROUP by Deptno; Efficiency will be higher than the following SELECT deptno, avg (SAL) from EMP WHERE Deptno in (a) GROUP by Deptno; Of course, if the filter conditions of a grouped query design group calculations, they can only be specified in the HAVING clause. 5. Sub-query optimization

I. Dynamic execution of SQLPREPARE from ' Delete from Test ' ; EXECUTE S1;Second, using cursorsDECLARE CURSOR for SELECT from FJDC. V_i_dg_dm_zy_wl_zbhz_attr T; OPEN V_cursor; FETCH into V_deletesql,v_insertsql; CLOSE V_cursor;Third, while loop while true -do expression ENDwhile;Iv. DB2 query table data, generate dynamic SQL, and execute1 CREATE PROCEDURE" TEST". " TEST "()2 BEGIN3

MySQL query optimization and MySQL Optimization1. Introduction A good web application has excellent access performance. MySQL database is an integral part of web applications and an important part that determines their performance. Therefore, it is vital to improve MySQL performance. MySQL performance improvement can be divided into three parts, including hardware, network, and software. The hardware and ne

there are usually several ways to tune a database: 1) Manual tuning. The main reliance on people, inefficient, requiring the operator to fully understand the principle of common sense depends on, but also the application, database management system, operating system and hardware have a broad and deep understanding. 2) Case-based tuning . This paper summarizes the recommended configuration values of database parameters and the design of